Zero Dark Thirty is one of the films most shrouded in secrecy in recent memory. The plot, about the hunt for Osama bin Laden, lends itself to secrecy. The research behind the script has been kept tightly under wraps, even as certain political forces launched allegations that the production team had improper access to confidential information. Even the poster graphics—featuring the title which, bonus secret, is military-speak for 12:30 am, the time at which SEAL Team Six breached bin Laden’s hide-out—suggest information that requires censorship, blacking-out, masking. We won’t spoil anything about what happens in the movie, but some of the people behind ZDT, due for wide release on Jan. 11, recently sat down in New York City to discuss the movie, and here are a few spilled secrets to quench your curiosity.

1. No, the U.S. government was not involved.

Director Kathryn Bigelow and screenwriter Mark Boal, who worked together on Oscar-winner The Hurt Locker, had already begun making a movie about the 2001 attempt to catch bin Laden in Tora Bora when, while they were scouting locations in Romania, they learned that bin Laden had been killed. Changing their story to encompass the decade-long hunt, they relied on Boal’s journalism background to source their research. That did not involve any access that a journalist might not get; Boal says that he went through the usual public-information and public-affairs agency branches to find out what he could about the raid.

2. There’s a reason we haven’t heard about the real-life people on whom the movie’s based.

Much of the movie’s plot is true: while the characters are inventions, they’re based on real people. But, even so, the real agents won’t be making appearances on any press tours. That’s because many of them, including the woman on whom Jessica Chastain’s character Maya is based, are currently working undercover. (Chastain didn’t even get to meet her.)

3. Jessica Chastain hung prop photos of the movie’s terrorists in her hotel room to get into character.

The actress, who nicknamed screenwriter Mark Boal “The Professor,” wanted to replicate Maya’s sense of being constantly surrounded by the men for whom she hunted. So she asked the prop department to make her extra copies of the photographs that hang in her character’s workspace.

4. The production team used decoy cameras and actors to shoot a major marketplace scene.

A big scene at a market was shot in India—only a few hours from Pakistan, so the architecture would match the city where the scene is meant to be—but it’s hard to shoot a movie in a crowded place without capturing a scene full of strangers staring into the lens. So, director Kathryn Bigelow would send a camera and actor a few hundred feet from the scene she wanted to film, in order to distract the crowd while she pulled off a stealthier shoot. You can get an extra half-hour unnoticed, the director says. And there were lots of decoy actors to choose from: the movie includes more than 100 speaking parts.

6. The compound where bin Laden is caught is a fully constructed replica of the real thing.

In order to film the complicated raid scene, Zero Dark Thirty producers built a real compound in Jordan, based on what they could learn from (diagrams and reporting) about the building where the CIA’s pursuit ended. The production designer—Jeremy Hindle, who has never made a feature film before—was responsible for making the building as real as possible. The cinder blocks with which the building was made, for example, were distressed so that they didn’t look new.

7. The helicopters used for the raid are also accurate replicas…maybe.

The stealth Black Hawks used by the Navy SEALs are so secret that nobody actually knows what they look like. For the production, four helicopters were created using basic helicopters with adaptations based on descriptions found during research. The stealth “skin” on the copters is CGI—but a dramatic near-accident during the flight scene is not: instead, the helicopter in question is hanging from a real, spinning crane.